1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same. In particular, the present invention relates to a semiconductor device having a fin field effect transistor including at least a first fin and a second fin.
2. Description of the Related Art
In a semiconductor device, e.g. a field effect transistor (FET) is provided as a semiconductor element used as a high-frequency amplifying element, switch element, or the like. An FET fabricated by using a compound semiconductor such as GaAs or InP is frequently employed because it can achieve high gain in the high-frequency region and is excellent in the linearity.
For the semiconductor device, miniaturization of the semiconductor element is required in order to enhance the integration degree. In the above-described FET, the gate length is becoming smaller for the miniaturization. However, this gate length decrease often causes characteristic deterioration such as the deterioration of the cut-off characteristic of the drain current attributed to the occurrence of the punch-through phenomenon due to the short-channel effect.
To suppress the occurrence of this problem, a fin field effect transistor (finFET) has been proposed (refer to e.g. Japanese Patent Laid-open No. 2002-118255).
In the finFET, a plate-shape fin including a channel forming region is so formed as to protrude from a substrate surface, and a gate electrode is so formed as to sandwich and cover both the side surfaces of the channel forming region in the fin. Therefore, the finFET can suppress the occurrence of the punch-through phenomenon due to the short-channel effect and enhance the cut-off characteristic of the drain current.
Furthermore, for the finFET, it is easy to form the desired number of fins per one gate electrode, and thus the drain current can be increased to the desired value. Therefore, if the finFET is formed as a multi-fin FET, it can be used as a high-frequency power element excellent in the maximum oscillation frequency fmax and the cut-off frequency fT.